Process of preparing h-acid



Patented May 22, 1928.

UNITED STATES PATENTVOFFICE.

IVAN GUBELMANN AND JOHN M. TINKER, OF SOUTH MILWAUKEE, WISCONSIN, AS- SIGNOBS TO. THE NEWPORT COMPANY, OF CARROLLVILLE, WISCONSIN, A COB/- POBATION DELAWARE PROCESS OF PREPARING H-ACID.

1V0 Drawing. Original application fled May 9, 1,925, November 4, 1925.

This invention relates to the preparation of H-acid or 1, 8-aminonaphthol-3, (i-disulfonic acid by the fusion with caustic alkalies of 1-naphthylamine-3, 6, 8-trisulphonic acid.

This application is a division of our application entitled Process of preparing 1-8- aminonaphthol sulphonic acid, Serial No. 29,215 filed May 9, 1925, issued as Patent No. 1,573,056, and relates back to the subiject-matter of that application.

The ordinary fusion with caustic alkalies of l-naphthylamine sulfonicacids containing a sulfonic acid group in the 8-position constitutes a well-known method by which 5 1, S-aminonaphthol sulfonic acids are generally prepared on a technical scale. We have found that by following methods in use heretofore considerable decomposition takes place, through the splitting off of ammonia, resulting in the formation as an impurity of 1, 8-dihydroxynaphthalene sulfonic acid. This decomposition not only lowers the yield but also causes the presence of undesirable impurities in the finished product. 2 The present invention, therefore, has for an object the production of 1, S-aminonaphthol sulfonic acids by an improvedmethod in which the fusion of l-naphthylamine sulfonic acids which contain a sulfonic acid 3 group in the 8-position is carried out with the least possible decomposition, resulting in excellent yields and a high quality of finished product.

Other and further important objects of this invention will be apparent from the disclosures in the following description, which sets forth the preferred form of our invention.

We have found that the fusion with caustic alkalies of the l-naphthylamine sulfonic acids proceeds very much more smoothly in the presence of ammonia. The presence of ammonia introduced prior to the caustic alkali fusion prevents almost entirel the splitting 5 off of ammonia formed by tie decomposition of the amino groups in the 1, 8-naphthylamine sulfonic acids used. We prefer to operate with ammonia pressures of from 7 5-150 lbs, but higher or lower pressures SerialNo. 29,215. Divided and this application filed Serial No. 66,755.

may be employed if desired. Without limitlng our invention to any particular procedure, the following example is given as illustrating the application of our improved method in a preferred form:

Charge an autoclave with 1000 lbs. water, 1000 lbs. caustic soda and 1000 lbs. 1-naphthylamine-3, 6, 8-trisu1fonic acid in the form of the di-sodium salt. After complete solution of the charged material, the autoclave is closed and 200 lbs. of 29% aqueousammonia is added. The temperature of the mixture is gradually raised to 173-17 6 C. ilnd maintained at that temperature for 2-3 IOUI'S. fusion mass is worked up by the usual methods, consisting of diluting, acidifying, filtering off the precipitate, and drying the same. This end product is a very pure 1, 8- aminonaphthol-3, 6-disulfonic acid in the form of its mono-sodium salt, commercially known as H-acid. The chemical formula for H-acid is OH NH:

Hso/ SOaH If the'H-acid made according to the foregoing process is analyzed, it will be found that the amount of 1, S-dihydroxynaphthalene sulfonic, acid present as impurity is After releasing the pressure, the

practically nil, which fact clearly demonstrates the value of the ammonia pressure used in our fusion method. The presence of ammonia prevents the splitting oifof the amino-group in the l-naphthylamine sulfonio acids, thereby causing higher yields and a distinctly improved quality of the finished product to be obtained.

We are aware that numerous details of the process may be varied through a wide range without departing from the spirit of this invention, and we do not desire limiting the patent granted other than as necessitated by the prior art.

We claim as our invention 1. The method of preparing 1, S-aminonaphthol-3, G-disulfonic acid, which includes the fusion with caustic alkalies of l-naphmonia pressure the ammonia being introthylamine-3, 6, 8-trisu1f0nic acid in the presduced prior to the fusion step. ence of added ammonia. In testimony whereof we have hereunto 10 2. The method of preparing 1, 8-aminosubscribed our names. 6 naphtho1-3, G-disulphonic acid, which consists in fusing 1-naphthy1amine-3, 6, 8-tri- IVAN GUBELMANN. sulfonic acid with caustic alkalies under am- JOHN M. TINKER. 

